The present invention relates to a hydraulic coupling for interconnecting hydraulic hoses or connecting hoses to various hydraulic fittings, such as adapters and the like.
A commonly used fitting, particularly in European countries, comprises a body having a threaded portion with a bore and an internal tapered seat. A fitting, which is adapted to be connected to a pipe or tubing, for example, is provided with a forwardly facing tapered external surface having a groove therein and an O-ring disposed within the groove. The fitting also includes a rearwardly facing shoulder which is engaged by a shoulder on a nut that encloses the fitting and is threadedly connected to the threaded portion of the body. As the nut is tightened on the threaded portion of the body, the fitting is advanced forwardly against the internal tapered seat and the O-ring is compressed to thereby form a fluid-tight seal.
A problem with this type of prior art fitting involves "nose collapse", which occurs when the externally tapered male fitting is driven down, under heavy torque, inside the tapered internal seat. The collapse of the nose of the male fitting is directly related to the amount of the linear travel of the fitting once engaged with the female tapered surface as a trigonometric function of the angle of the taper. In such European style fittings, the taper is typically 12.degree. relative to the axis, although there is also a 30.degree. configuration.
If the installer tightens the fitting beyond the point where the tapered surfaces meet and the O-ring is compressed, the annular portion of the male fitting in the area of the groove and O-ring will be collapsed inwardly, thereby damaging the fitting and thereby restricting the flow of the fluid medium.